Two central questions of alcoholism etiology research are 1) how to characterize the different pathways by which problem drinking develops and 2) how to account for differences among these pathways. The purpose of this proposal is to contribute to the understanding of alcohol use disorders by examining the heterogeneity of alcohol trajectories that occurs from adolescence to young adulthood. Specifically, in an attempt to examine the ongoing, dynamic and interactive nature of the critical developmental period of highest alcoholism risk, this study will a) identify the various alcohol use trajectories as related to historical factors (e.g., family history of alcohol, parenting practices, childhood psychopathology) and b) characterize the transitions in severity within trajectories as related to more proximal effects (e.g., onset of comorbid psychopathology, antecedents to drinking) that influence the progression and/or moderation in problem drinking. Efforts to replicate and extend findings from the extant literature will be accomplished by: 1) use of high risk sample (by virtue of familial history of alcoholism) whereby higher rates of problem drinking are expected to occur, 2) use of prospective and retrospective data from drinking onset to age 26 allowing for investigation of the critical time point when drinking declines or develops into dependent drinking, 3) use of multiple data analysis techniques to validate and differentiate previous studies and 4) integration of drinking trajectories and transitions with associated historical and proximal factors. Understanding the pathways of alcohol use, the numerous factors placing individuals at risk for continued problem drinking, and the processes that may protect against or promote problem drinking during potentially sensitive periods are essential steps towards guiding future research, prevention, and treatment efforts.